Induction + STC-1000?

[Mer-man]

Has anyone built an induction-heated recirculation system?

The idea is to recirculate from under a false bottom while the pot sits on an induction burner that is activated by a controller, e.g. STC-1000.

My only concern is the additional complexity of induction burners' control circuitry. I am unclear about whether it can be set to maximum and switched on and off as desired. My guess is no without some rewiring.

(Searching did not turn up a result.)


I do see that there are some simple, dial-based controlled induction cooktops. But has anyone done it?

 

[Mer-man]

Thanks, I guess automation is the right forum.

 

[RufusBrewer]

I assume the induction heater comes with a low to high knob.

Your controller has a PWM (or similar) output. You will use this PWM out put to control an SSR, which will in turn controls the heat level of the induction heater.

I expect that you will always keep the level knob on the heater to maximum. Let the controller do all the up-down adjustments. To use them simultaneously, the SSR will turn the power down, then the control knob on the heater will turn it down some more.

Could be dificult to get repeatable results and you might confuse your controller.

Bottom line: When using the PID, I would set the level on the heater to high. If you are using the PID in bypass, it is OK to ride the heater knob.

 

[raysmithtx]

I can't use a stc1000 with my induction heater because every time the stc switches, it drops all power to the unit. I then have to press the "on" button to get it back on. Every induction system I have seen operate this way.

 

[Mer-man]

I am not married to the stc, it is just what I have on hand.

What would be the best solution for repeatability?

 

[RufusBrewer]

Now that it has been pointed, this makes sense. You do not want a heating unit turn on when you plug it in. Smart safety feature.

One possible option is bypass the On/Off circuit. That requires expertise, knowledge, voiding the warranty of your heater and a willingness to assume the risk that comes with bypassing a safety feature.

You could create a circuit with relay contacts in parallel with the heater's On switch. It duplicates the function of the the heater's On switch that act per the PID's programming. Easier said than done.

 

[alphaomega]

External control of induction hobs has been done before.
Like this, on a german forum for example.
The 'manual knob' type heaters seems to be easier. I'd advise against going to crazy, as I know of a few people who have blown the control boards of their heaters trying to interface them with a microcontroller. Even if you do measure 5v for control logic, I wouldn't assume it safe to connect directly to a micro.
Also, even if you use a manual knob stove, you shouldn't switch mains directly. It has a cooling fan that needs to run even after switching off.

 

[Mer-man]

Nice, but he is doing some fancy USB thing.

Would it not suffice to leave the internal circuitry alone (i.e. fan, etc) and just use an STC to switch the knob circuit on/off at full to maintain mash?

I'm thinking to have the STC wired in after the knob so it can break the circuit when the temp is adequate.
I would just have the pump run at something like half-speed.

Then when not mashing, I could use the knob to adjust as needed (i.e. to maintain a boil) but the STC circuit would stay closed if the sensor reported low temp (because the recirculation loop would be closed off and cooling.)

Thoughts?

 

[alphaomega]

Absolutely!
That would work just fine!
The knob has an on/off line and the pot value. The trick is to route the on/off line to the outside with a 3.5mm (audio) plug, that is normally closed. That way the hob will function normally when a plug is not inserted. Then route a male plug to the heating relay of the stc, insert it in the female plug and set the pot to desired power and let the stc control on/off.

Cheers!

 

[Mer-man]

Smart, I get it.
Looks like 3500w should be ok for me (up to 35L).
Any shopping suggestions? Specifically around the diameter needed, about 30cm.

 

[alphaomega]

Yeah, I that Hendi hob (3.5kW) that is referenced in that german thread myself. I use it with a 36L Patina pot. Both the diameter and weight (when full) is off by quite some bit from the manufacturers recommended maximum. Still, neither of this seems to be cause any problems.
That is just one of those things I don't regret buying

 

[alphaomega]

You might be interested in this thread I started on a swedish forum. I guess the pictures are pretty self explanatory. Just note I made an error in the first post, you need a 4-pin JST XH extension cable.

 

[BridgewaterBrewer]

Can an STC-1000 handle 3500W?

 

[Weezy]

I hadn't thought this was possible since I believed the signal, with power, from the microcontroller to the coil was some wave form and not simply on/off power. Perhaps there are models out there with circuitry that can accept a hacked in on/off signal? I can't read German and the Swedish link went to an empty forum page. Very interesting though.

I had modified my avantco induction cooker by making the internal temp sensor into an external sensor that could be put into a thermosetting in the side of the pot. This allows for the induction cookers internal temp sensors to work very accurately. But temp choices are limited. I have a thread on here somewhere. I'll dig it up and put it in my Sig.

 

[alphaomega]

@BridgewaterBrewer: No, it can't. But it doesn't have to, it can be used to control the on/off signal to the induction hob in the case of the Hendi. That is just a 5v logic signal.

@Weezy: The link works fine for me.